The number of people choosing a plant-based diet is growing steadily, some adopting the pattern of eating out of concerns for animal welfare or the environment and others for health reasons. For ethical vegans (those more concerned with animal welfare and the environment), the quality of the foods may not be as important as the fact that they were not produced with animal sources.

But is simply cutting out animal products enough to improve your health? A huge new study from the Harvard School of Public Health answered this question, demonstrating the drastic impact of "healthy" and "unhealthy" plant-based diets on the risk for heart disease.

Plant-based diets and heart health.

Researchers collected data from over 200,000 health professionals without heart disease who were followed for 25 years. They filled out repeated food questionnaires, and a dietary pattern called healthful plant-based diet index (hPDI) was defined as those eating whole grains, fruits and vegetables, nuts, legumes, teas, coffee, and vegetable oils. Another dietary pattern, called an unhealthful PDI (uPDI), was defined as one with increases in juices, sweetened beverages, grains, sweets, fried potatoes. In other words: a junk food vegan diet.

During the study, 8,631 subjects developed coronary heart disease (CHD). Adhering to a plant-based diet lowered the risk of CHD by about 8 percent overall, but this relationship was much stronger for those following the hPDI, which slashed the risk of CHD by 25 percent. Those following the uPDI pattern actually developed more CHD, with an increased risk of as much as 30 percent!

Quality food matters.

A database this large and over so many years is uncommon and provides important insight into what we should be putting on our plates. The overall finding that plant-based diets lower the risk of CHD is not new, but this mega study helps cement this idea. The importance of the effect of the quality of the plant-based diet on actual measures of life and death is also dramatically demonstrated in this study.

The food industry has responded with many plant-based processed food and drink choices that would easily fit the uPDI pattern, and they should be avoided or enjoyed rarely. The majority of the food we eat should be from the produce department at local stores, the farmers market plant-based choices, or our own gardens. For health, the quality of the food we choose—in a plant-based diet and in any other pattern—is the primary driver of the health benefits. I prefer the term "plant diet" over "plant-based" to make it clear that it should be plants, not food made in factory plants, that fuel our health.